Imaging lens

ABSTRACT

There is provided an imaging lens with high resolution which satisfies in well balance the low-profileness and the low F-number and properly corrects aberrations. 
     An imaging lens comprises a first lens having positive refractive power, a second lens having the positive refractive power, a third lens, a fourth lens, a fifth lens being a double-sided aspheric lens, and a sixth lens being double-sided aspheric lens and having a concave surface facing the image side near the optical axis, wherein the image-side surface of the sixth lens is an aspheric surface changing to the convex surface at a peripheral area.

The present application is based on and claims priority of a Japanesepatent application No. 2017-106027 filed on May 29, 2017, the entirecontents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an imaging lens which forms an image ofan object on a solid-state image sensor such as a CCD sensor or a C-MOSsensor used in an imaging device, and more particularly to an imaginglens which is built in an imaging device mounted in an increasinglycompact and low-profile smartphone and mobile phone, an informationterminal such as a PDA (Personal Digital Assistant), a game console, PCand a robot, and moreover, a home appliance and an automobile withcamera function.

Description of the Related Art

In recent years, it becomes common that camera function is mounted in ahome appliance, information terminal equipment, an automobile and publictransportation. Demand of products with the camera function is moreincreased, and development of products is being made accordingly.

The imaging lens mounted in such equipment is required to be compact andhave high-resolution performance. For Example, Patent Document 1(JP2012-155223A) and Patent Document 2 (JP2016-114803) disclose theimaging lens comprising six lenses.

Patent Document 1 discloses an imaging lens comprising, in order from anobject side, a first lens group having positive refractive power, secondlens group having negative refractive power, a third lens group havingthe positive refractive power, a fourth lens group having the negativerefractive power, a fifth lens group having the positive refractivepower, and a sixth lens group having the negative refractive power.

Patent Document 2 discloses an imaging lens comprising, in order from anobject side, a first lens having a convex surface facing the object sideand positive refractive power, a second lens having negative refractivepower, a third lens having the convex surface facing the object side, afourth lens having the positive refractive power, a fifth lens havingthe negative refractive power, and a sixth lens having the negativerefractive power.

However, in lens configurations disclosed in the above-described PatentDocuments 1 and 2, when low-profileness and low F-number are to berealized, it is very difficult to correct aberration at a peripheralarea, and excellent optical performance can not be obtained.

The present invention has been made in view of the above-describedproblems, and an object of the present invention is to provide animaging lens with high resolution which satisfies in well balance thelow-profileness and the low F-number and excellently correctsaberrations.

Regarding terms used in the present invention, a convex surface, aconcave surface or a plane surface of lens surfaces implies that a shapeof the lens surface near an optical axis (paraxial portion), refractivepower implies the refractive power near the optical axis (paraxialportion). The pole point implies an off-axial point on an asphericsurface at which a tangential plane intersects the optical axisperpendicularly. The total track length is defined as a distance alongthe optical axis from an object-side surface of an optical elementlocated closest to the object to an image plane, when thickness of an IRcut filter or a cover glass which may be arranged between the imaginglens and the image plane is regarded as an air.

An imaging lens according to the present invention which forms an imageof an object on a solid-state image sensor, comprises in order from anobject side to an image side, a first lens having positive refractivepower, a second lens having the positive refractive power, a third lens,a fourth lens, a fifth lens being a double-sided aspheric lens, and asixth lens being a double-sided aspheric lens and having a concavesurface facing the image side near the optical axis, wherein theimage-side surface of the sixth lens is an aspheric surface changing tothe convex surface at a peripheral area.

In the above-described configuration, the first lens achieveslow-profileness and wide field of view of the imaging lens by thepositive refractive power. The second lens has the positive refractivepower, achieves the low-profileness and wide field of view of theimaging lens, and properly corrects astigmatism and field curvature. Thethird lens and the fourth lens maintain the low-profileness and properlycorrect aberrations such as spherical aberration, coma aberration,astigmatism and field curvature in well balance. The fifth lens is thedouble-sided aspheric lens, and therefore reduces burden on the sixthlens which corrects the field curvature and the distortion, and controlslight ray incident angle to the image sensor. The sixth lens maintainsthe low-profileness and secures back focus. Furthermore, the sixth lensis the double-sided aspheric lens, and therefore corrects the fieldcurvature and the distortion, and controls the light ray incident angleto the image sensor.

According to the imaging lens of the above-described configuration, itis preferable that a below conditional expression (1) is satisfied:

1.5<vd4/vd5<3.6  (1)

wherevd4: abbe number at d-ray of a fourth lens, andvd5: abbe number at d-ray of a fifth lens.

The conditional expression (1) defines relationship between the abbenumbers at d-ray of the fourth lens and the fifth lens, and is acondition for properly correcting chromatic aberration of magnification.By satisfying the conditional expression (1), the chromatic aberrationof magnification is properly corrected.

According to the imaging lens of the above-described configuration, itis preferable that a below conditional expression (2) is satisfied:

0.30<(T3/TTL)×100<0.85  (2)

whereT3: distance along an optical axis from an image-side surface of thethird lens to an object-side surface of the fourth lens, andTTL: distance along an optical axis from an object-side surface of thefirst lens to an image plane.

The conditional expression (2) defines an appropriate scope of thedistance along an optical axis from the image-side surface of the thirdlens to the object-side surface of the fourth lens, and is a conditionfor achieving the low-profileness and proper aberration correction. Bysatisfying the conditional expression (2), total track length can beshortened, the light ray incident angle to the fourth lens becomesappropriate, and excessive occurrence of the spherical aberration, thecoma aberration and the distortion is suppressed.

According to the imaging lens of the above-described configuration, itis preferable that a below conditional expression (3) is satisfied:

0.5<vd1/(vd2+vd3)<1.0  (3)

wherevd1: abbe number at d-ray of a first lens,vd2: abbe number at d-ray of a second lens, andvd3: abbe number at d-ray of a third lens.

The conditional expression (3) defines relationship between the abbenumbers at d-ray of the first lens, the second lens and the third lens,and is a condition for properly correcting axial chromatic aberration.By satisfying the conditional expression (3), the axial chromaticaberration is more properly corrected.

According to the imaging lens of the above-described configuration, itis preferable that the second lens has a biconvex shape having convexsurfaces facing the object side and the image side near the opticalaxis, or a meniscus shape having a concave surface facing the objectside near the optical axis.

When the second lens has the biconvex shape near the optical axis, thepositive refractive power can be appropriately allocated to theobject-side surface and the image-side surface. Therefore, largepositive refractive power can be provided while suppressing occurrenceof the spherical aberration. As a result, the imaging lens can achievefurther low-profileness and wide field of view.

On the other hand, when the second lens has the meniscus shape having aconcave surface facing the object side near the optical axis, the lightray incident angle to the second lens can be appropriately controlled,and the coma aberration and high-order spherical aberration are properlycorrected.

According to the imaging lens of the above-described configuration, itis preferable that the fourth lens has the positive refractive power.Furthermore, a shape of the fourth lens is preferably the biconvex shapehaving convex surfaces facing the object side and the image side nearthe optical axis, or a meniscus shape having a concave surface facingthe object side near the optical axis.

When the fourth lens has the biconvex shape near the optical axis, thepositive refractive power can be appropriately allocated to theobject-side surface and the image-side surface. Therefore, largepositive refractive power can be provided while suppressing occurrenceof the spherical aberration. As a result, the imaging lens can achievefurther low-profileness and wide field of view.

On the other hand, when the fourth lens has the meniscus shape having aconcave surface facing the object side near the optical axis, the lightray incident angle to the fourth lens can be appropriately controlled,and the coma aberration and the high-order spherical aberration areproperly corrected.

According to the imaging lens of the above-described configuration, itis preferable that a below conditional expression (4) is satisfied:

1.35<f1/f<3.30  (4)

wheref1: focal length of the first lens, andf: focal length of the overall optical system.

The conditional expression (4) defines the refractive power of the firstlens, and is a condition for achieving the low-profileness and theproper aberration correction. When a value is below the upper limit ofthe conditional expression (4), the positive refractive power of thefirst lens becomes appropriate, and the low-profileness is facilitated.On the other hand, when the value is above the lower limit of theconditional expression (4), the high-order spherical aberration and thecoma aberration can be properly corrected.

According to the imaging lens of the above-described configuration, itis preferable that a below conditional expression (5) is satisfied:

0.8<f2/f<3.4  (5)

wheref2: focal length of the second lens, andf: focal length of the overall optical system.

The conditional expression (5) defines the refractive power of thesecond lens, and is a condition for achieving the low-profileness andthe proper aberration correction. When a value is below the upper limitof the conditional expression (5), the positive refractive power of thesecond lens becomes appropriate, and the low-profileness is facilitated.On the other hand, when the value is above the lower limit of theconditional expression (5), the high-order spherical aberration and thecoma aberration can be properly corrected.

According to the imaging lens of the above-described configuration, itis preferable that a below conditional expression (6) is satisfied:

−1.70<f3/f<0.65  (6)

wheref3: focal length of the third lens, andf: focal length of the overall optical system.

The conditional expression (6) defines the refractive power of the thirdlens, and is a condition for reducing sensitivity to manufacturing errorand for properly correcting the distortion. When the refractive power ofthe third lens is not large or small more than necessary, thesensitivity to manufacturing error can be reduced and the comaaberration and the distortion at a peripheral area can be properlycorrected.

According to the imaging lens of the above-described configuration, itis preferable that a below conditional expression (7) is satisfied:

0.65<f4/f<2.10  (7)

wheref4: focal length of the fourth lens, andf: focal length of the overall optical system.

The conditional expression (7) defines the refractive power of thefourth lens, and is a condition for achieving the low-profileness andthe proper aberration correction. When a value is below the upper limitof the conditional expression (7), the positive refractive power of thefourth lens becomes appropriate, and the low-profileness can beachieved. On the other hand, when the value is above the lower limit ofthe conditional expression (7), the high-order spherical aberration andthe coma aberration can be properly corrected.

According to the imaging lens of the above-described configuration, itis preferable that a below conditional expression (8) is satisfied:

1.9<|f6|/f  (8)

wheref6: focal length of the sixth lens, andf: focal length of the overall optical system.

The conditional expression (8) defines the refractive power of the sixthlens, and is a condition for achieving the low-profileness and theproper aberration correction. When the value is above the lower limit ofthe conditional expression (8), the chromatic aberration is corrected,the total track length is shortened and the field curvature can beproperly corrected.

According to the imaging lens of the above-described configuration, itis preferable that the fifth lens has plane surfaces on both sides nearthe optical axis, and has no substantial refractive power near theoptical axis.

When the fifth lens has plane surfaces on both side near the opticalaxis, and has no substantial refractive power near the optical axis, theaberrations such as the chromatic aberration of magnification can beproperly corrected without affecting the focal length of the overalloptical system or allocation of the refractive power of other lenses.

The fifth lens is not limited to a shape having plane surfaces on theboth sides near the optical axis. If effect on the focal length of theoverall optical system or the refractive power of each lens issuppressed to small, various shapes may be applicable for the fifthlens, such as a meniscus shape having the convex surface facing theobject side, a biconvex shape having the convex surfaces facing theobject side and the image side, a meniscus shape having the concavesurface facing the object side, a biconcave shape having the concavesurfaces facing the object side and the image side, a shape having aplane surface facing the object side and a convex or a concave surfacefacing the image side, and a shape having the plane surface facing theimage side and the convex or the concave surface facing the object side.

According to the imaging lens of the above-described configuration, itis preferable that a below conditional expression (9) is satisfied:

0.1<D6/ΣD<0.3  (9)

whereD6: thickness on the optical axis of the sixth lens, andΣD: total sum of thickness on the optical axis of the first lens, thesecond lens, the third lens, the fourth lens, the fifth lens and thesixth lens.

The conditional expression (9) defines the thickness on the optical axisof the sixth lens to the total sum of each thickness on the optical axisof the first lens to the sixth lens, and is a condition for achievingimprovement of formability and proper aberration correction. Bysatisfying the conditional expression (9), the thickness of the sixthlens becomes appropriate, and uneven thickness of a center area and aperipheral area of the sixth lens becomes small. As a result, theformability of the sixth lens can be improved. Furthermore, bysatisfying the conditional expression (9), the thickness on the opticalaxis of the first to the fifth lenses and intervals therebetween can beappropriately determined, and freedom in the aspheric surface isimproved. Therefore, the proper aberration correction can be made.

According to the imaging lens of the above-described configuration, itis preferable that a below conditional expression (10) is satisfied:

0.7<Σ(L1F−L6R)/f<1.6  (10)

whereΣ(L1F−L6R): distance along the optical axis from the object-side surfaceof the first lens to the image-side surface of the sixth lens, andf: focal length of the overall optical system.

The conditional expression (10) defines the distance along the opticalaxis from the object-side surface of the first lens to the image-sidesurface of the sixth lens to the focal length of the overall opticalsystem, and is a condition for achieving the low-profileness and properaberration correction. When a value is below the upper limit of theconditional expression (10), the back focus is secured and space forarranging a filter is also secured. On the other hand, when the value isabove the lower limit of the conditional expression (10), thickness ofeach lens of which the imaging lens is comprised is easily secured.Furthermore, each interval of lenses can be appropriately determined,and therefore the freedom in the aspheric surface is improved.Therefore, the proper aberration correction can be made.

According to the imaging lens of the above-described configuration, itis preferable that a shape of the third lens is a meniscus shape havingthe concave surface facing the object side near the optical axis.Furthermore, it is more preferable that a below conditional expression(11) is satisfied:

0.1<r5/r6<0.7  (11)

wherer5: paraxial curvature radius of the object-side surface of the thirdlens, andr6: paraxial curvature radius of the image-side surface of the thirdlens.

The conditional expression (11) defines relationship of the curvatureradii of the object-side surface and the image-side surface of the thirdlens, and is a condition for properly correcting the aberrations. Whenthe shape near the optical axis of the third lens is the meniscus shapesatisfying a scope of the conditional expression (11), the comaaberration and the astigmatism can be properly corrected.

According to the imaging lens of the above-described configuration, itis preferable that below conditional expressions (12) and (13) aresatisfied:

0.20<r11/f<0.55  (12)

0.15<r12/f<0.45  (13)

wherer11: paraxial curvature radius of the object-side surface of the sixthlens,r12: paraxial curvature radius of the image-side surface of the sixthlens, and f: focal length of the overall optical system.

The conditional expressions (12) and (13) define a shape near theoptical axis of the sixth lens, and are conditions for securing the backfocus and achieving the low-profileness. By satisfying the conditionalexpressions (12) and (13), appropriate back focus is secured and thelow-profileness can be achived.

According to the imaging lens of the above-described configuration, itis preferable that a below conditional expression (14) is satisfied:

Fno≤2.0

where

Fno: F-number.

The conditional expression (14) defines the F-number. When a value isbelow the upper limit of the conditional expression (14), brightnessrequired for the imaging lens in recent years can be fully secured, ifit is mounted in a portable mobile device, a monitoring camera, or anonboard camera.

According to the imaging lens of the above-described configuration, itis preferable that a below conditional expression (15) is satisfied:

0.6<f2/f4<2.6  (15)

wheref2: focal length of the first lens, andf4: focal length of the fourth lens.

The conditional expression (15) defines an appropriate scope of a ratiobetween the refractive power of the second lens and the refractive powerof the fourth lens, and a condition for achieving the low-profilenessand the proper aberration correction. By satisfying the conditionalexpression (15), the large refractive power is appropriately balanced tothe second lens and the fourth lens, the low-profileness and the widefield of view is achieved, and proper correction of the astigmatism andthe field curvature can be made.

According to the imaging lens of the above-described configuration, itis preferable that a below conditional expression (16) is satisfied:

0.60<T3/T4<1.35  (16)

whereT3: distance along an optical axis from an image-side surface of thethird lens to an object-side surface of the fourth lens, andT4: distance along an optical axis from an image-side surface of thefourth lens to an object-side surface of the fifth lens.

The conditional expression (16) defines a ratio of an interval betweenthe third lens and the fourth lens, and an interval between the fourthlens and the fifth lens, and is a condition for achieving thelow-profileness and the proper aberration correction. By satisfying theconditional expression (16), difference between the interval of thethird lens and the fourth lens and the interval of the fourth lens andthe fifth lens is suppressed not to be increased, and thelow-profileness is achieved. Furthermore, by satisfying the conditionalexpression (16), the fourth lens is arranged at an optimum position, andaberration correction function of the lens becomes more effective.

According to the imaging lens of the above-described configuration, itis preferable that a below conditional expression (17) is satisfied:

5<(D5/TTL)×100<12  (17)

whereD5: thickness on the optical axis of the fifth lens, andTTL: distance along an optical axis from an object-side surface of thefirst lens to an image plane.

The conditional expression (17) defines an appropriate thickness on theoptical axis of the fifth lens, and is a condition for maintainingproper formability of the fifth lens and achieving the low-profileness.

When a value is below the upper limit of the conditional expression(17), the thickness on the optical axis of the fifth lens is preventedfrom being excessively large, and securing an air gap of the object sideand the image side of the fifth lens is facilitated. Therefore, thelow-profileness can be maintained. On the other hand, when the value isabove the lower limit of the conditional expression (17), the thicknesson the optical axis of the fifth lens is prevented from beingexcessively small, and the formability of the lens becomes proper.

Effect of Invention

According to the present invention, there can be provided an imaginglens with high resolution which satisfies in well balance thelow-profileness and the low F-number, and properly corrects aberrations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a general configuration of an imaginglens in Example 1 according to the present invention;

FIG. 2 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 1 according to the present invention;

FIG. 3 is a schematic view showing the general configuration of animaging lens in Example 2 according to the present invention;

FIG. 4 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 2 according to the present invention;

FIG. 5 is a schematic view showing the general configuration of animaging lens in Example 3 according to the present invention;

FIG. 6 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 3 according to the present invention;

FIG. 7 is a schematic view showing the general configuration of animaging lens in Example 4 according to the present invention;

FIG. 8 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 4 according to the present invention.

FIG. 9 is a schematic view showing a general configuration of an imaginglens in Example 5 according to the present invention;

FIG. 10 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 5 according to the present invention;

FIG. 11 is a schematic view showing the general configuration of animaging lens in Example 6 according to the present invention;

FIG. 12 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 6 according to the present invention;

FIG. 13 is a schematic view showing the general configuration of animaging lens in Example 7 according to the present invention; and

FIG. 14 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 7 according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, the preferred embodiment of the present invention will bedescribed in detail referring to the accompanying drawings.

FIGS. 1, 3, 5, 7, 9, 11 and 13 are schematic views of the imaging lensesin Examples 1 to 7 according to the embodiments of the presentinvention, respectively.

As shown in FIG. 1, the imaging lens according to the presentembodiments comprises in order from an object side to an image side, afirst lens L1 having positive refractive power, a second lens L2 havingthe positive refractive power, a third lens L3, a fourth lens L4, afifth lens L5 being a double-sided aspheric lens, and a sixth lens L6having a concave surface facing the image side near the optical axis X.The image-side surface of the sixth lens L6 is an aspheric surfacechanging to the convex surface at a peripheral area.

A filter IR such as an IR cut filter and a cover glass are arrangedbetween the sixth lens L6 and an image plane IMG. The filter IR isomissible.

The first lens L1 has the positive refractive power, and occurrence ofaberrations is suppressed by aspheric surfaces on both sides andlow-profileness and wide field of view of the imaging lens are achieved.The first lens L1 has a meniscus shape having a convex surface facingthe object side near the optical axis X, or a biconvex shape havingconvex surfaces facing the object side and the image side near theoptical axis X. In an Example shown in FIG. 1, an Example 2 shown inFIG. 3, an Example 3 shown in FIG. 5, an Example 5 shown in FIG. 9 andan Example 7 shown in FIG. 13, the first lens L1 has the meniscus shapehaving the convex surface facing the object side near the optical axisX. In this case, a position of principal point on the image side of theimaging lens moves toward the object side, and it is advantageous forthe low-profileness. In an Example 4 shown in FIG. 7 and an Example 6shown in FIG. 11, the first lens L1 has the biconvex shape having theconvex surfaces facing the object side and the image side near theoptical axis X. In this case, the position of principal point on theimage side of the imaging lens moves toward the image side, and it isadvantageous for the wide field of view.

The second lens L2 has the positive refractive power, and astigmatismand field curvature are properly corrected by aspheric surfaces on bothsides and the low-profileness and the wide field of view of the imaginglens are achieved. The second lens L2 has the biconvex shape having theconvex surfaces facing the object side and the image side near theoptical axis X, or a meniscus shape having a concave surface facing theobject side near the optical axis X. In the Example 1 shown in FIG. 1,the Example 2 shown in FIG. 3, the Example 3 shown in FIG. 5, theExample 4 shown in FIG. 7 and the Example 7 shown in FIG. 13, the secondlens L2 has the biconvex shape having the convex surfaces facing theobject side and the image side near the optical axis X. In this case,the positive refractive power is appropriately allocated to theobject-side surface and the image-side surface. Therefore, largepositive refractive power can be provided while suppressing occurrenceof the spherical aberration. As a result, the imaging lens can achievefurther low-profileness and wide field of view. In the Example 5 shownin FIG. 9 and the Example 6 shown in FIG. 11, the second lens L2 has themeniscus shape having a concave surface facing the object side near theoptical axis X. In this case, the light ray incident angle to the secondlens L2 can be appropriately controlled, and the coma aberration andhigh-order spherical aberration are properly corrected.

The third lens L3 has negative refractive power, and the sphericalaberration, the coma aberration, the astigmatism and the chromaticaberration are properly corrected by the aspheric surfaces on bothsides. A shape of the third lens L3 is the meniscus shape having aconcave surface facing the object side near the optical axis X.Therefore, the light ray incident angle to the third lens L3 can beappropriately controlled, and the coma aberration and the high-orderspherical aberration are properly corrected.

The fourth lens L4 has the positive refractive power, and theastigmatism and the field curvature are properly corrected by theaspheric surfaces on both sides and the low-profileness and the widefield of view of the imaging lens are achieved. The fourth lens L4 hasthe biconvex shape having the convex surfaces facing the object side andthe image side near the optical axis X, or the meniscus shape having theconcave surface facing the object side near the optical axis X. In theExample 1 shown in FIG. 1, the Example 2 shown in FIG. 3, the Example 3shown in FIG. 5, the Example 4 shown in FIG. 7, the Example 5 shown inFIG. 9 and the Example 6 shown in FIG. 11, the fourth lens L4 has thebiconvex shape near the optical axis X. In this case, the positiverefractive power is appropriately allocated to the object-side surfaceand the image-side surface. Therefore, the large positive refractivepower can be provided while suppressing occurrence of the sphericalaberration. As a result, the imaging lens can achieve furtherlow-profileness and wide field of view. In the Example 7 shown in FIG.13, the fourth lens L4 has the meniscus shape having the concave surfacefacing the object side near the optical axis X. In this case, the lightray incident angle to the fourth lens L4 can be appropriatelycontrolled, and the coma aberration and the high-order sphericalaberration are properly corrected.

The fifth lens L5 reduces burden on the sixth lens L6 which corrects thefield curvature and the distortion and controls light ray incident angleto the image sensor, and also corrects chromatic aberration ofmagnification by the aspheric surfaces on the both sides. The fifth lensL5 has plane surfaces on both sides near the optical axis X, and is anaberration correction lens having no substantial refractive power nearthe optical axis X. Therefore, the aberrations can be properly correctedwithout affecting the focal length of the overall optical system orallocation of the refractive power of other lenses. The fifth lens L5 isnot limited to the double-sided plane surface shape near the opticalaxis X. If effect on the focal length of the overall optical system orthe refractive power of each lens is suppressed to small, various shapesmay be applicable for the fifth lens L5, such as a meniscus shape havingthe convex surface facing the object side, a biconvex shape having theconvex surfaces facing the object side and the image side, a meniscusshape having the concave surface facing the object side, a biconcaveshape having the concave surfaces facing the object side and the imageside, a shape having a plane surface facing the object side and a convexor a concave surface facing the image side, and a shape having the planesurface facing the image side and the convex or the concave surfacefacing the object side.

The sixth lens L6 has the concave surface facing the image side near theoptical axis X and the negative refractive power, and secures back focuswhile maintaining the low-profileness. The refractive power of the sixthlens L6 may be the positive refractive power as shown in the Example 7shown in FIG. 13. Furthermore, correction of the field curvature and thedistortion, and control of light ray incident angle to the image sensorare made by the aspheric surfaces on the both sides. The image-sidesurface of the sixth lens L6 is the aspheric surface having a pole pointand changes to the convex surface at an area apart from the optical axisX and maintains the convex shape until an edge of an effective diameter.By applying such aspheric surface, correction of the field curvature andcontrol of light ray angle to an image sensor are facilitated.

In the imaging lens according to the present invention, an aperture stopST is arranged on the object side of the first lens L1. By arranging theaperture stop ST closest to the object, a position of entrance pupilgets away from the image plane, and control of the light ray incidentangle to the image sensor and telecentricity becomes facilitated.

Regarding the imaging lens according to the present embodiments, forexample as shown in FIG. 1, all lenses of the first lens L1 to the sixthlens L6 are preferably single lenses which are not cemented each other.Configuration without the cemented lens can frequently use the asphericsurfaces, and proper correction of the aberrations can be realized.Furthermore, workload for cementing is reduced, and manufacturing in lowcost becomes possible.

Regarding the imaging lens according to the present embodiments, aplastic material is used for all of the lenses, and manufacturing isfacilitated and mass production in a low cost can be realized. Both-sidesurfaces of all lenses are appropriate aspheric, and the aberrations arefavorably corrected.

The material applied to the lens is not limited to the plastic material.By using glass material, further high performance may be aimed. All ofsurfaces of lenses are preferably formed as aspheric surfaces, however,spherical surfaces may be adopted which is easy to manufacture inaccordance with required performance.

The imaging lens according to the present embodiments shows preferableeffect by satisfying the below conditional expressions (1) to (17).

1.5<vd4/vd5<3.6  (1)

0.30<(T3/TTL)×100<0.85  (2)

0.5<vd1/(vd2+vd3)<1.0  (3)

1.35<f1/f<3.30  (4)

0.8<f2/f<3.4  (5)

−1.70<f3/f<−0.65  (6)

0.65<f4/f<2.10  (7)

1.9<|f6|/f  (8)

0.1<D6/ΣD<0.3  (9)

0.7<Σ(L1F−L6R)/f<1.6  (10)

0.1<r5/r6<0.7  (11)

0.20<r11/f<0.55  (12)

0.15<r12/f<0.45  (13)

Fno≤2.0  (14)

0.6<f2/f4<2.6  (15)

0.60<T3/T4<1.35  (16)

5<(D5/TTL)×100<12  (17)

wherevd1: abbe number at d-ray of a first lens L1,vd2: abbe number at d-ray of a second lens L2,vd3: abbe number at d-ray of a third lens L3,vd4: abbe number at d-ray of a fourth lens L4,vd5: abbe number at d-ray of a fifth lens L5,T3: distance along an optical axis from an image-side surface of thethird lens L3 to an object-side surface of the fourth lens L4,T4: distance along an optical axis from an image-side surface of thefourth lens L4 to an object-side surface of the fifth lens L5,TTL: distance along an optical axis from an object-side surface of thefirst lens L1 to an image plane,f: focal length of the overall optical system,f1: focal length of the first lens L1,f2: focal length of the second lens L2,f3: focal length of the third lens L3,f4: focal length of the fourth lens L4,f6: focal length of the sixth lens L6,D5: thickness on the optical axis of the fifth lens L5,D6: thickness on the optical axis of the sixth lens L6,ΣD: total sum of thickness on the optical axis X of the first lens L1,the second lens L2, the third lens L3, the fourth lens L4, the fifthlens L5 and the sixth lens L6,Σ(L1F−L6R): distance along the optical axis X from the object-sidesurface of the first lens L1 to the image-side surface of the sixth lensL6,r5: paraxial curvature radius of the object-side surface of the thirdlens L3,r6: paraxial curvature radius of the image-side surface of the thirdlens L3,r11: paraxial curvature radius of the object-side surface of the sixthlens L6,r12: paraxial curvature radius of the image-side surface of the sixthlens L6, and

Fno: F-number.

It is not necessary to satisfy the above all conditional expressions,and by satisfying the conditional expression individually, operationaladvantage corresponding to each conditional expression can be obtained.

The imaging lens according to the present embodiments shows furtherpreferable effect by satisfying the below conditional expressions (1a)to (17a).

1.85<vd4/vd5<3.20  (1a)

0.40<(T3/TTL)×100<0.75  (2a)

0.60<vd1/(vd2+vd3)<0.85  (3a)

1.65<f1/f<2.90  (4a)

1.00<f2/f<2.95  (5a)

−1.5<f3/f<−0.8  (6a)

0.80<f4/f<1.85  (7a)

2.4<|f6|/f<20.0  (8a)

0.14<D6/ΣD<0.25  (9a)

0.9<Σ(L1F−L6R)/f<1.4  (10a)

0.13<r5/r6<0.60  (11a)

0.24<r11/f<0.45  (12a)

0.20<r12/f<0.35  (13a)

Fno≤1.9  (14a)

0.75<f2/f4<2.3  (15a)

0.75<T3/T4<1.20  (16a)

6<(D5/TTL)×100<10  (17a)

The signs in the above conditional expressions have the same meanings asthose in the paragraph before the preceding paragraph.

In this embodiment, the aspheric shapes of the surfaces of the asphericlens are expressed by Equation 1, where Z denotes an axis in the opticalaxis direction, H denotes a height perpendicular to the optical axis, Rdenotes a curvature radius, k denotes a conic constant, and A4, A6, A8,A10, A12, A14, A16, A18 and A20 denote aspheric surface coefficients.

$\begin{matrix}{Z = {\frac{\frac{H^{2}}{R}}{1 + \sqrt{1 - {( {k + 1} )\frac{{II}^{2}}{R^{2}}}}} + {\Lambda_{4}{H^{4}++}\Lambda_{6}H^{6}} + {\Lambda_{8}H^{8}} + {\Lambda_{10}H^{10}} + {\Lambda_{12}H^{12}} + {\Lambda_{14}H^{14}} + {\Lambda_{16}H^{16}} + {\Lambda_{18}H^{18}} + {\Lambda_{20}H^{20}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Next, examples of the imaging lens according to this embodiment will beexplained. In each example, f denotes the focal length of the overalloptical system of the imaging lens, Fno denotes an F-number, ω denotes ahalf field of view, and ih denotes a maximum image height. Additionally,i denotes surface number counted from the object side, r denotes acurvature radius, d denotes the distance of lenses along the opticalaxis (surface distance), Nd denotes a refractive index at d-ray(reference wavelength), and vd denotes an abbe number at d-ray. As foraspheric surfaces, an asterisk (*) is added after surface number i.

EXAMPLE 1

The basic lens data is shown below in Table 1.

TABLE 1 Example 1 Unit mm f = 2.72 ih = 3.26 Fno = 1.8 TTL = 4.11 ω(°) =50.1 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number νd (Object) Infinity Infinity 1(Stop) Infinity −0.0510  2* 2.2524 0.4131 1.544 55.86 (vd1)  3* 5.36920.1174  4* 6.0879 0.4526 1.535 55.66 (vd2)  5* −2.3793 0.3515  6*−0.7310 0.3300 1.661 20.37 (vd3)  7* −1.4661 0.0260  8* 10.0989 0.38251.544 55.86 (vd4)  9* −2.3572 0.0300 10* Infinity 0.3600 1.614 25.58(vd5) 11* Infinity 0.0334 12* 1.0843 0.4918 1.535 55.66 (vd6) 13* 0.86140.5000 14  Infinity 0.2100 1.517 64.20 15  Infinity 0.4818 Image PlaneInfinity Constituent Lens Data Lens Start Surface Focal Length 1 2 6.8102 4 3.259 3 6 −2.686 4 8 3.550 5 10 Infinity 6 12 −33.885 AsphericSurface Data Second Surface Third Surface Fourth Surface Fifth SurfaceSixth Surface Seventh Surface k −2.331179E+00   0.000000E+00−1.000000E+00 −9.999999E−01 −1.000000E+00   0.000000E+00 A4 −7.527715E−02 −2.220918E−01 −1.512366E−01 −1.504052E−01   7.168343E−02−8.029630E−02 A6    2.319407E−02 −8.729089E−02 −2.817847E−01  1.138025E−02 −7.631071E−01 −3.797023E−01 A8  −2.762643E−01−6.155922E−01 −1.869433E−01 −3.627602E−01   3.243245E+00   2.386234E+00A10   0.000000E+00   7.070838E−01 −8.875539E−02 −4.029084E−01−6.825057E+00 −4.836478E+00 A12   0.000000E+00   0.000000E+00  4.416396E−01   2.133227E+00   7.731701E+00   5.042076E+00 A14  0.000000E+00   0.000000E+00   0.000000E+00 −2.637456E+00 −4.665493E+00−2.735304E+00 A16   0.000000E+00   0.000000E+00   0.000000E+00  1.077927E+00   1.329231E+00   6.183892E−01 A18   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00 A20   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00 Eighth Surface NinthSurface Tenth Surface Eleventh Surface Twelfth Surface ThirteenthSurface k −1.186726E+01 −5.494574E+00   0.000000E+00   0.000000E+00−1.749347E+00 −6.224194E+00 A4  −5.858264E−01 −1.765618E−01  8.845825E−01   1.230193E+00 −1.898125E−01 −2.683399E−02 A6   1.714607E+00   8.112415E−01 −1.924596E+00 −2.751103E+00 −8.109097E−03−9.674510E−02 A8  −2.741997E+00 −1.751492E+00   2.291965E+00  3.353928E+00 −1.072885E−01   9.456732E−02 A10   2.709759E+00  2.347716E+00 −1.836641E+00 −2.645794E+00   2.127916E−01 −4.148820E−02A12 −1.725241E+00 −1.916429E+00   1.045465E+00   1.383599E+00−1.392192E−01   1.029346E−02 A14   6.799612E−01   9.003401E−01−4.350007E−01 −4.715054E−01   4.558670E−02 −1.491162E−03 A16−1.588798E−01 −2.213776E−01   1.248930E−01   9.966130E−02 −8.140478E−03  1.162402E−04 A18   1.837638E−02   2.196511E−02 −2.120587E−02−1.178062E−02   7.602449E−04 −3.548513E−06 A20   0.000000E+00  0.000000E+00   1.550254E−03   5.927364E−04 −2.916836E−05 −2.250417E−08

The imaging lens in Example 1 satisfies conditional expressions (1) to(17) as shown in Table 8.

FIG. 2 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 1. The spherical aberration diagramshows the amount of aberration at wavelengths of F-ray (486 nm), d-ray(588 nm), and C-ray (656 nm). The astigmatism diagram shows the amountof aberration at d-ray on a sagittal image surface S and on tangentialimage surface T, respectively (same as FIGS. 4, 6, 8, 10, 12 and 14). Asshown in FIG. 2, each aberration is corrected excellently.

EXAMPLE 2

The basic lens data is shown below in Table 2.

TABLE 2 Example 2 Unit mm f = 2.66 ih = 3.26 Fno = 1.8 TTL = 4.09 ω(°) =49.9 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number νd (Object) Infinity Infinity 1(Stop) Infinity −0.0510  2* 2.2559 0.3923 1.544 55.86 (vd1)  3* 6.34360.1209  4* 9.5000 0.4886 1.535 55.66 (vd2)  5* −2.5193 0.3838  6*−0.7424 0.2421 1.661 20.37 (vd3)  7* −1.5132 0.0200  8* 12.0245 0.45561.544 55.86 (vd4)  9* −1.9696 0.0200 10* Infinity 0.3635 1.614 25.58(vd5) 11* Infinity 0.0451 12* 1.0176 0.5421 1.535 55.66 (vd6) 13* 0.79090.5000 14  Infinity 0.2100 1.517 64.20 15  Infinity 0.3742 Image PlaneInfinity Constituent Lens Data Lens Start Surface Focal Length 1 2 6.2222 4 3.777 3 6 −2.521 4 8 3.145 5 10 Infinity 6 12 −39.776 AsphericSurface Data Second Surface Third Surface Fourth Surface Fifth SurfaceSixth Surface Seventh Surface k −2.695462E+00   0.000000E+00−3.119093E+01 −1.335637E−01 −9.278509E−01   0.000000E+00 A4 −7.527715E−02 −2.220918E−01 −1.512366E−01 −1.504052E−01   7.168343E−02−8.029630E−02 A6    2.319407E−02 −8.729089E−02 −2.817847E−01  1.138025E−02 −7.631071E−01 −3.797023E−01 A8  −2.762643E−01−6.155922E−01 −1.869433E−01 −3.627602E−01   3.243245E+00   2.386234E+00A10   0.000000E+00   7.070838E−01 −8.875539E−02 −4.029084E−01−6.825057E+00 −4.836478E+00 A12   0.000000E+00   0.000000E+00  4.416396E−01   2.133227E+00   7.731701E+00   5.042076E+00 A14  0.000000E+00   0.000000E+00   0.000000E+00 −2.637456E+00 −4.665493E+00−2.735304E+00 A16   0.000000E+00   0.000000E+00   0.000000E+00  1.077927E+00   1.329231E+00   6.183892E−01 A18   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00 A20   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00 Eighth Surface NinthSurface Tenth Surface Eleventh Surface Twelfth Surface ThirteenthSurface k   9.780001E+01 −3.361475E+00   0.000000E+00   0.000000E+00−1.804938E+00 −4.974734E+00 A4  −5.779474E−01 −1.493699E−01  9.373616E−01   1.235279E+00 −1.996052E−01 −2.768815E−02 A6   1.778412E+00   7.726362E−01 −1.985774E+00 −2.741133E+00 −1.225109E−02−9.625771E−02 A8  −3.077586E+00 −1.755397E+00   2.356057E+00  3.329674E+00 −1.069381E−01   9.673744E−02 A10   3.239769E+00  2.345984E+00 −1.898728E+00 −2.635137E+00   2.133280E−01 −4.256441E−02A12 −2.138360E+00 −1.914744E+00   1.074841E+00   1.382481E+00−1.392405E−01   1.040494E−02 A14   7.708789E−01   9.001788E−01−4.374730E−01 −4.716857E−01   4.556365E−02 −1.474588E−03 A16−1.003858E−01 −2.228034E−01   1.215196E−01   9.969614E−02 −8.139113E−03  1.151275E−04 A18 −9.792236E−03   2.278357E−02 −1.973163E−02−1.178015E−02   7.604543E−04 −4.077100E−06 A20   0.000000E+00  0.000000E+00   1.335666E−03   5.924430E−04 −2.917784E−05  2.624107E−08

The imaging lens in Example 2 satisfies conditional expressions (1) to(17) as shown in Table 8.

FIG. 4 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 2. As shown in FIG. 4, eachaberration is corrected excellently.

EXAMPLE 3

The basic lens data is shown below in Table 3.

TABLE 3 Example 3 Unit mm f = 2.59 ih = 3.26 Fno = 1.8 TTL = 3.94 ω(°) =51.2 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number νd (Object) Infinity Infinity 1(Stop) Infinity −0.0510  2* 2.4369 0.3986 1.544 55.86 (vd1)  3* 9.00000.0927  4* 9.6512 0.4716 1.535 55.66 (vd2)  5* −2.5036 0.3223  6*−0.8138 0.2759 1.661 20.37 (vd3)  7* −1.6670 0.0200  8* 7.4351 0.45831.544 55.86 (vd4)  9* −1.7587 0.0200 10* Infinity 0.3458 1.614 25.58(vd5) 11* Infinity 0.0673 12* 1.0121 0.4133 1.535 55.66 (vd6) 13* 0.68990.5000 14  Infinity 0.2100 1.517 64.20 15  Infinity 0.4145 Image PlaneInfinity Constituent Lens Data Lens Start Surface Focal Length 1 2 6.0112 4 3.768 3 6 −2.762 4 8 2.660 5 10 Infinity 6 12 −7.325 AsphericSurface Data Second Surface Third Surface Fourth Surface Fifth SurfaceSixth Surface Seventh Surface k −3.260016E+00   0.000000E+00−3.782225E+01 −1.826789E+00 −1.081000E+00   0.000000E+00 A4 −7.527715E−02 −2.220918E−01 −1.512366E−01 −1.504052E−01   7.168343E−02−8.029630E−02 A6    2.319407E−02 −8.729089E−02 −2.817847E−01  1.138025E−02 −7.631071E−01 −3.797023E−01 A8  −2.762643E−01−6.155922E−01 −1.869433E−01 −3.627602E−01   3.243245E+00   2.386234E+00A10   0.000000E+00   7.070838E−01 −8.875539E−02 −4.029084E−01−6.825057E+00 −4.836478E+00 A12   0.000000E+00   0.000000E+00  4.416396E−01   2.133227E+00   7.731701E+00   5.042076E+00 A14  0.000000E+00   0.000000E+00   0.000000E+00 −2.637456E+00 −4.665493E+00−2.735304E+00 A16   0.000000E+00   0.000000E+00   0.000000E+00  1.077927E+00   1.329231E+00   6.183892E−01 A18   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00 A20   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00 Eighth Surface NinthSurface Tenth Surface Eleventh Surface Twelfth Surface ThirteenthSurface k   3.262137E+01 −6.046067E+00   0.000000E+00   0.000000E+00−1.761221E+00 −4.174866E+00 A4  −5.161471E−01 −1.232851E−01  8.568401E−01   1.246105E+00 −2.136159E−01 −6.128761E−02 A6   1.553392E+00   7.682042E−01 −1.716235E+00 −2.748763E+00 −4.537272E−03−8.416284E−02 A8  −2.600186E+00 −1.723019E+00   1.863763E+00  3.331651E+00 −1.109148E−01   9.542871E−02 A10   2.835580E+00  2.275904E+00 −1.443339E+00 −2.638124E+00   2.149159E−01 −4.285154E−02A12 −2.213846E+00 −1.864006E+00   8.795010E−01   1.384832E+00−1.394310E−01   1.048277E−02 A14   1.186491E+00   8.995568E−01−4.454881E−01 −4.721943E−01   4.553733E−02 −1.476898E−03 A16−3.846535E−01 −2.312642E−01   1.634907E−01   9.966285E−02 −8.137865E−03  1.140672E−04 A18   5.504336E−02   2.441071E−02 −3.454872E−02−1.175873E−02   7.620464E−04 −3.944055E−06 A20   0.000000E+00  0.000000E+00   3.003970E−03   5.906561E−04 −2.935038E−05  2.110647E−08

The imaging lens in Example 3 satisfies conditional expressions (1) to(17) as shown in Table 8.

FIG. 6 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 3. As shown in FIG. 6, eachaberration is corrected excellently.

EXAMPLE 4

The basic lens data is shown below in Table 4.

TABLE 4 Example 4 Unit mm f = 2.47 ih = 3.26 Fno = 1.8 TTL = 3.91 ω(°) =52.5 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number νd (Object) Infinity Infinity 1(Stop) Infinity 0.0300  2* 2.6539 0.4608 1.544 55.86 (vd1)  3* −500.35070.1044  4* 100.0701 0.4194 1.535 55.66 (vd2)  5* −2.4843 0.3152  6*−0.7912 0.2001 1.661 20.37 (vd3)  7* −1.6698 0.0200  8* 8.3903 0.59241.544 55.86 (vd4)  9* −1.4881 0.0200 10* Infinity 0.3013 1.614 25.58(vd5) 11* Infinity 0.1237 12* 0.9144 0.4126 1.535 55.66 (vd6) 13* 0.62900.5000 14  Infinity 0.2100 1.517 64.20 15  Infinity 0.3059 Image PlaneInfinity Constituent Lens Data Lens Start Surface Focal Length 1 2 4.8522 4 4.539 3 6 −2.503 4 8 2.372 5 10 Infinity 6 12 −7.597 AsphericSurface Data Second Surface Third Surface Fourth Surface Fifth SurfaceSixth Surface Seventh Surface k −2.632580E+00   0.000000E+00  0.000000E+00 −7.917237E+00 −1.045405E+00   0.000000E+00 A4 −7.511897E−02 −2.216251E−01 −1.509188E−01 −1.500892E−01   7.153280E−02−8.012757E−02 A6    2.311290E−02 −8.698540E−02 −2.807985E−01  1.134042E−02 −7.604364E−01 −3.783734E−01 A8  −2.749116E−01−6.125782E−01 −1.860280E−01 −3.609841E−01   3.227366E+00   2.374550E+00A10   0.000000E+00   7.026358E−01 −8.819706E−02 −4.003738E−01−6.782123E+00 −4.806053E+00 A12   0.000000E+00   0.000000E+00  4.382463E−01   2.116837E+00   7.672297E+00   5.003336E+00 A14  0.000000E+00   0.000000E+00   0.000000E+00 −2.613524E+00 −4.623159E+00−2.710484E+00 A16   0.000000E+00   0.000000E+00   0.000000E+00  1.066649E+00   1.315324E+00   6.119193E−01 A18   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00 A20   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00 Eighth Surface NinthSurface Tenth Surface Eleventh Surface Twelfth Surface ThirteenthSurface k   4.042719E+01 −3.636609E+00   0.000000E+00   0.000000E+00−1.929494E+00 −3.388291E+00 A4  −4.933426E−01 −1.337301E−01  9.546355E−01   1.293156E+00 −2.437873E−01 −9.762711E−02 A6   1.439113E+00   7.387064E−01 −1.772673E+00 −2.747973E+00   3.950192E−03−6.599258E−02 A8  −2.452508E+00 −1.708771E+00   1.904511E+00  3.308634E+00 −1.120200E−01   9.399156E−02 A10   2.779103E+00  2.303112E+00 −1.488840E+00 −2.632469E+00   2.153171E−01 −4.434269E−02A12 −2.202493E+00 −1.886041E+00   9.071041E−01   1.385081E+00−1.396150E−01   1.109211E−02 A14   1.141336E+00   9.077591E−01−4.495010E−01 −4.722948E−01   4.556846E−02 −1.582081E−03 A16−3.382970E−01 −2.354152E−01   1.624357E−01   9.964229E−02 −8.139940E−03  1.226534E−04 A18   4.202373E−02   2.562746E−02 −3.582932E−02−1.174936E−02   7.625235E−04 −4.218023E−06 A20   0.000000E+00  0.000000E+00   3.578610E−03   5.893388E−04 −2.941679E−05  2.268033E−08

The imaging lens in Example 4 satisfies conditional expressions (1) to(17) as shown in Table 8.

FIG. 8 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 4. As shown in FIG. 8, eachaberration is corrected excellently.

EXAMPLE 5

The basic lens data is shown below in Table 5.

TABLE 5 Example 5 Unit mm f = 2.49 ih = 3.26 Fno = 1.8 TTL = 3.91 ω(°) =52.1 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number νd (Object) Infinity Infinity 1(Stop) Infinity −0.0300  2* 2.6123 0.4432 1.544 55.86 (vd1)  3* 59.99990.1006  4* −5999.9940 0.4177 1.535 55.66 (vd2)  5* −2.3939 0.3248  6*−0.7724 0.2050 1.661 20.37 (vd3)  7* −1.6285 0.0200  8* 8.1679 0.56401.544 55.86 (vd4)  9* −1.4563 0.0200 10* Infinity 0.2820 1.614 25.58(vd5) 11* Infinity 0.1322 12* 0.8988 0.3839 1.535 55.66 (vd6) 13* 0.62850.5000 14  Infinity 0.2100 1.517 64.20 15  Infinity 0.3734 Image PlaneInfinity Constituent Lens Data Lens Start Surface Focal Length 1 2 5.0042 4 4.478 3 6 −2.458 4 8 2.319 5 10 Infinity 6 12 −7.741 AsphericSurface Data Second Surface Third Surface Fourth Surface Fifth SurfaceSixth Surface Seventh Surface k −3.702824E+00   0.000000E+00  0.000000E+00 −6.448212E+00 −1.080022E+00   0.000000E+00 A4 −7.527738E−02 −2.220925E−01 −1.512371E−01 −1.504057E−01   7.168365E−02−8.029654E−02 A6    2.319419E−02 −8.729133E−02 −2.817861E−01  1.138030E−02 −7.631109E−01 −3.797042E−01 A8  −2.762662E−01−6.155966E−01 −1.869446E−01 −3.627628E−01   3.243268E+00   2.386251E+00A10   0.000000E+00   7.070902E−01 −8.875619E−02 −4.029120E−01−6.825119E+00 −4.836522E+00 A12   0.000000E+00   0.000000E+00  4.416444E−01   2.133251E+00   7.731786E+00   5.042131E+00 A14  0.000000E+00   0.000000E+00   0.000000E+00 −2.637490E+00 −4.665554E+00−2.735339E+00 A16   0.000000E+00   0.000000E+00   0.000000E+00  1.077943E+00   1.329251E+00   6.183985E−01 A18   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00 A20   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00 Eighth Surface NinthSurface Tenth Surface Eleventh Surface Twelfth Surface ThirteenthSurface k   3.367314E+01 −3.768192E+00   0.000000E+00   0.000000E+00−1.948663E+00 −3.298325E+00 A4  −5.004754E−01 −1.192848E−01  9.830686E−01   1.299255E+00 −2.452653E−01 −1.107272E−01 A6   1.469749E+00   7.226936E−01 −1.835626E+00 −2.757331E+00   4.277730E−03−5.860955E−02 A8  −2.524711E+00 −1.682018E+00   1.989508E+00  3.316366E+00 −1.101479E−01   9.126892E−02 A10   2.871435E+00  2.267117E+00 −1.557904E+00 −2.634591E+00   2.144441E−01 −4.380031E−02A12 −2.265235E+00 −1.858146E+00   9.354133E−01   1.384890E+00−1.394668E−01   1.104958E−02 A14   1.163429E+00   8.997934E−01−4.490824E−01 −4.721300E−01   4.555141E−02 −1.584185E−03 A16−3.441692E−01 −2.379676E−01   1.579797E−01   9.967033E−02 −8.135783E−03  1.225808E−04 A18   4.340716E−02   2.701494E−02 −3.449233E−02−1.177166E−02   7.616982E−04 −4.090529E−06 A20   0.000000E+00  0.000000E+00   3.448965E−03   5.920393E−04 −2.935678E−05  1.337399E−08

The imaging lens in Example 5 satisfies conditional expressions (1) to(17) as shown in Table 8.

FIG. 10 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 5. As shown in FIG. 10,each aberration is corrected excellently.

EXAMPLE 6

The basic lens data is shown below in Table 6.

TABLE 6 Example 6 Unit mm f = 2.50 ih = 3.26 Fno = 1.8 TTL = 3.92 ω(°) =52.3 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number νd (Object) Infinity Infinity 1(Stop) Infinity −0.0300  2* 2.6952 0.4499 1.544 55.86 (vd1)  3*−500.0000 0.0992  4* −236.5491 0.4213 1.535 55.66 (vd2)  5* −2.41520.3264  6* −0.7681 0.2000 1.661 20.37 (vd3)  7* −1.6067 0.0200  8*7.8466 0.5631 1.544 55.86 (vd4)  9* −1.4775 0.0200 10* Infinity 0.28891.614 25.58 (vd5) 11* Infinity 0.1274 12* 0.9109 0.3914 1.535 55.66(vd6) 13* 0.6369 0.5000 14  Infinity 0.2100 1.517 64.20 15  Infinity0.3697 Image Plane Infinity Constituent Lens Data Lens Start SurfaceFocal Length 1 2 4.927 2 4 4.560 3 6 −2.461 4 8 2.334 5 10 Infinity 6 12−7.879 Aspheric Surface Data Second Surface Third Surface Fourth SurfaceFifth Surface Sixth Surface Seventh Surface k −4.497389E+00  0.000000E+00   0.000000E+00 −6.219467E+00 −1.064692E+00   0.000000E+00A4  −7.527715E−02 −2.220918E−01 −1.512366E−01 −1.504052E−01  7.168343E−02 −8.029630E−02 A6    2.319407E−02 −8.729089E−02−2.817847E−01   1.138025E−02 −7.631071E−01 −3.797023E−01 A8 −2.762643E−01 −6.155922E−01 −1.869433E−01 −3.627602E−01   3.243245E+00  2.386234E+00 A10   0.000000E+00   7.070838E−01 −8.875539E−02−4.029084E−01 −6.825057E+00 −4.836478E+00 A12   0.000000E+00  0.000000E+00   4.416396E−01   2.133227E+00   7.731701E+00  5.042076E+00 A14   0.000000E+00   0.000000E+00   0.000000E+00−2.637456E+00 −4.665493E+00 −2.735304E+00 A16   0.000000E+00  0.000000E+00   0.000000E+00   1.077927E+00   1.329231E+00  6.183892E−01 A18   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00 A20   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00 Eighth Surface Ninth Surface Tenth Surface EleventhSurface Twelfth Surface Thirteenth Surface k   3.360683E+01−3.721259E+00   0.000000E+00   0.000000E+00 −1.879843E+00 −3.336148E+00A4  −5.054708E−01 −1.270644E−01   9.605790E−01   1.288821E+00−2.477514E−01 −1.049799E−01 A6    1.483371E+00   7.519021E−01−1.791143E+00 −2.753188E+00   5.308238E−03 −6.111112E−02 A8 −2.528776E+00 −1.705370E+00   1.923993E+00   3.316318E+00 −1.109453E−01  9.174578E−02 A10   2.872815E+00   2.277352E+00 −1.501562E+00−2.635934E+00   2.145576E−01 −4.378499E−02 A12 −2.285687E+00−1.864225E+00   9.104191E−01   1.385387E+00 −1.394541E−01   1.103457E−02A14   1.185696E+00   8.981698E−01 −4.468369E−01 −4.721497E−01  4.555319E−02 −1.582184E−03 A16 −3.492906E−01 −2.325064E−01  1.593117E−01   9.963342E−02 −8.136690E−03   1.219252E−04 A18  4.255337E−02   2.514587E−02 −3.468565E−02 −1.175503E−02   7.617190E−04−3.933179E−06 A20   0.000000E+00   0.000000E+00   3.449503E−03  5.896842E−04 −2.935663E−05   1.801413E−09

The imaging lens in Example 6 satisfies conditional expressions (1) to(17) as shown in Table 8.

FIG. 12 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 6. As shown in FIG. 12,each aberration is corrected excellently.

EXAMPLE 7

The basic lens data is shown below in Table 7.

TABLE 7 Example 7 Unit mm f = 2.81 ih = 3.26 Fno = 1.8 TTL = 4.25 ω(°) =50.0 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number νd (Object) Infinity Infinity 1(Stop) Infinity −0.0325  2* 2.6482 0.4779 1.544 55.86 (vd1)  3* 21.31670.2448  4* 4.4669 0.4057 1.535 55.66 (vd2)  5* −26.3020 0.2268  6*−2.0213 0.3000 1.661 20.37 (vd3)  7* −13.4597 0.0208  8* −10.3341 0.47831.544 55.86 (vd4)  9* −2.0235 0.0200 10* Infinity 0.3600 1.661 20.37(vd5) 11* Infinity 0.0264 12* 0.7824 0.4857 1.535 55.66 (vd6) 13* 0.67820.5000 14  Infinity 0.2100 1.517 64.20 15  Infinity 0.5669 Image PlaneInfinity Constituent Lens Data Lens Start Surface Focal Length 1 2 5.5062 4 7.173 3 6 −3.638 4 8 4.531 5 10 Infinity 6 12 15.253 AsphericSurface Data Second Surface Third Surface Fourth Surface Fifth SurfaceSixth Surface Seventh Surface k   2.472955E+00   0.000000E+00−1.000000E+00 −9.999999E−01 −1.000000E+00   0.000000E+00 A4 −9.148951E−02 −1.626906E−01 −1.643676E−01 −1.499051E−01 −5.784550E−01−2.334739E−02 A6  −1.003969E−02 −1.270262E−01 −1.405476E−02−8.795773E−03   1.580392E+00 −2.640383E−02 A8  −1.175108E−01  6.505164E−02 −4.758153E−01 −5.995714E−01 −4.789919E+00 −1.621203E+00A10   0.000000E+00 −2.950093E−02   3.913980E−01   6.759232E−01  9.854858E+00   4.023703E+00 A12   0.000000E+00   0.000000E+00  0.000000E+00 −1.271616E−01 −1.118269E+01 −3.926083E+00 A14  0.000000E+00   0.000000E+00   0.000000E+00   2.139518E−02  6.626144E+00   1.752123E+00 A16   0.000000E+00   0.000000E+00  0.000000E+00 −3.626468E−02 −1.604280E+00 −2.944286E−01 A18  0.000000E+00   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00   0.000000E+00 A20   0.000000E+00   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00   0.000000E+00 EighthSurface Ninth Surface Tenth Surface Eleventh Surface Twelfth SurfaceThirteenth Surface k −1.232784E+01 −3.360798E+01   0.000000E+00  0.000000E+00 −2.148448E+00 −2.508419E+00 A4    6.137630E−01−2.488437E−01   7.583641E−01   5.726725E−01 −2.862441E−01 −2.262405E−01A6  −1.040908E+00   1.208180E+00 −1.191706E+00 −7.104699E−01  4.475700E−02   1.007643E−01 A8    8.735916E−01 −1.912512E+00  1.064228E+00   4.208414E−01   1.595003E−02 −2.624835E−02 A10−4.017928E−01   1.470622E+00 −6.563438E−01 −1.561038E−01 −5.046308E−03  3.943571E−03 A12   8.951159E−02 −6.019950E−01   2.467789E−01  3.653295E−02   2.044365E−04 −3.099407E−04 A14 −2.211894E−03  1.267435E−01 −4.839913E−02 −4.788211E−03   5.760857E−05   7.457861E−06A16 −2.863722E−03 −1.088079E−02   3.723050E−03   2.605478E−04−4.902575E−06   2.946515E−07 A18   0.000000E+00   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00   0.000000E+00 A20  0.000000E+00   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00   0.000000E+00

The imaging lens in Example 7 satisfies conditional expressions (1) to(17) as shown in Table 8.

FIG. 14 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 7. As shown in FIG. 14,each aberration is corrected excellently.

In table 8, values of conditional expressions (1) to (17) related to theExamples 1 to 7 are shown.

TABLE 8 Conditional Expression Example1 Example2 Example3 Example4Example5 Example6 Example7  (1) vd4/vd5 2.18 2.18 2.18 2.18 2.18 2.182.74  (2) (T3/TTL)*100 0.63 0.49 0.51 0.51 0.51 0.51 0.49  (3)vd1/(vd2 + vd3) 0.73 0.73 0.73 0.73 0.73 0.73 0.73  (4) f1/f 2.51 2.342.32 1.97 2.01 1.97 1.96  (5) f2/f 1.20 1.42 1.45 1.84 1.79 1.82 2.56 (6) f3/f −0.99 −0.95 −1.07 −1.01 −0.99 −0.98 −1.30  (7) f4/f 1.31 1.181.03 0.96 0.93 0.93 1.61  (8) |f6|/f 12.47 14.96 2.83 3.08 3.10 3.155.43  (9) D6/ΣD 0.20 0.22 0.17 0.17 0.17 0.17 0.19 (10) Σ(L1F − L6R)/f1.10 1.16 1.11 1.20 1.16 1.16 1.09 (11) r5/r6 0.50 0.49 0.49 0.47 0.470.48 0.15 (12) r11/f 0.40 0.38 0.39 0.37 0.36 0.36 0.28 (13) r12/f 0.320.30 0.27 0.25 0.25 0.25 0.24 (14) Fno 1.80 1.80 1.80 1.80 1.80 1.801.80 (15) f2/f4 0.92 1.20 1.42 1.91 1.93 1.95 1.58 (16) T3/T4 0.87 1.001.00 1.00 1.00 1.00 1.04 (17) (D5/TTL)*100 8.76 8.89 8.78 7.70 7.22 7.388.47

When the imaging lens according to the present invention is adopted to aproduct with the camera function, there is realized contribution to thelow-profileness and the low F-number of the camera and also highperformance thereof.

DESCRIPTION OF REFERENCE NUMERALS

ST: aperture stop,L1: first lens,L2: second lens,L3: third lens,L4: fourth lens,L5: fifth lens,L6: sixth lens,IMG: image plane,IR: filter, andih: maximum image height.

1-20. (canceled)
 21. An imaging lens comprising in order from an objectside to an image side, a stop, a first lens having positive refractivepower, a second lens, a third lens, a fourth lens, a fifth lens being adouble-sided aspheric lens and has plane surfaces on both sides near anoptical axis, and a sixth lens being a double-sided aspheric lens andhaving a concave surface facing the image side near the optical axis,wherein an image-side surface of said sixth lens is an aspheric surfacechanging to the convex surface at a peripheral area.
 22. The imaginglens according to claim 21, wherein a second lens having the positiverefractive power.
 23. The imaging lens according to claim 21, whereinbelow conditional expressions (1) and (2) are satisfied:5<vd4/vd5<3.6  (1)0.30<(T3/TTL)×100<0.85  (2) where vd4: abbe number at d-ray of a fourthlens, vd5: abbe number at d-ray of a fifth lens, T3: distance along anoptical axis from an image-side surface of the third lens to anobject-side surface of the fourth lens, and TTL: distance along anoptical axis from an object-side surface of the first lens to an imageplane.
 24. The imaging lens according to claim 21, wherein a belowconditional expression (3) is satisfied:0.5<vd1/(vd2+vd3)<1.0 where vd1: abbe number at d-ray of a first lens,vd2: abbe number at d-ray of a second lens, and vd3: abbe number atd-ray of a third lens.
 25. The imaging lens according to claim 21,wherein said second lens has a biconvex shape near the optical axis. 26.The imaging lens according to claim 21, wherein said second lens has ameniscus shape having a concave surface facing the object side near theoptical axis.
 27. The imaging lens according to claim 21, wherein saidfourth lens has a biconvex shape near the optical axis.
 28. The imaginglens according to claim 21, wherein said fourth lens has a meniscusshape having a concave surface facing the object side near the opticalaxis.
 29. The imaging lens according to claim 21, wherein a belowconditional expression (4) is satisfied:1.35<f1/f<3.30   (4) where f1: focal length of the first lens, and f:focal length of the overall optical system.
 30. The imaging lensaccording to claim 21, wherein a below conditional expression (5) issatisfied:0.8<f2/f<3.4  (5) where f2: focal length of the second lens, and f:focal length of the overall optical system.
 31. The imaging lensaccording to claim 21, wherein a below conditional expression (6) issatisfied:−1.70<f3/f<−0.65  (6) where f3: focal length of the third lens, and f:focal length of the overall optical system.
 32. The imaging lensaccording to claim 21, wherein a below conditional expression (7) issatisfied:0.65<f4/f<2.10  (7) where f4: focal length of the fourth lens, and f:focal length of the overall optical system.
 33. The imaging lensaccording to claim 21, wherein a below conditional expression (8) issatisfied:1.9<|f6|/f  (8) where f6: focal length of the sixth lens, and f: focallength of the overall optical system.
 34. The imaging lens according toclaim 21, wherein said fifth lens has plane surfaces on both sides nearthe optical axis.
 35. The imaging lens according to claim 21, wherein abelow conditional expression (9) is satisfied:0.1<D6/ΣD<0.3  (9) where D6: thickness on the optical axis of the sixthlens, and ΣD: total sum of thickness on the optical axis of the firstlens, the second lens, the third lens, the fourth lens, the fifth lensand the sixth lens.
 36. The imaging lens according to claim 21, whereina below conditional expression (10) is satisfied:0.7</(L1F−L6R)/f<1.6  (10) where Σ(L1F−L6R): distance along the opticalaxis from the object-side surface of the first lens to the image-sidesurface of the sixth lens, and f: focal length of the overall opticalsystem.
 37. The imaging lens according to claim 21, wherein a belowconditional expression (11) is satisfied:0.1<r5/r6<0.7  (11) where r5: paraxial curvature radius of theobject-side surface of the third lens, and r6: paraxial curvature radiusof the image-side surface of the third lens.
 38. The imaging lensaccording to claim 21, wherein a below conditional expressions (12) and(13) are satisfied:0.20<r11/f<0.55  (12)0.15<r12/f<0.45  (13) where r11: paraxial curvature radius of theobject-side surface of the sixth lens, r12: paraxial curvature radius ofthe image-side surface of the sixth lens, and f: focal length of theoverall optical system.
 39. The imaging lens according to claim 21,wherein a below conditional expression (14) is satisfied:Fno≤2.0  (14) where Fno: F-number.
 40. The imaging lens according toclaim 21, wherein a below conditional expression (15) is satisfied:0.6<f2/f4<2.6  (15) where f2: focal length of the second lens, and f4:focal length of the fourth lens.